Piggybacked Pyrolyzer and Thermal Oxidizer

ABSTRACT

A pyrolysis waste treatment system having a pyrolyzer and a thermal oxidizer that are aligned in a partially or completely piggybacked fashion, and heat from the exhaust gas of the thermal oxidizer is shunted back to the pyrolyzer to help sustain pyrolysis. Such conduits can have any suitable configuration, including for example where the conduit extends from sides (as opposed to the ends) of each of the pyrolyzer and the thermal oxidizer. Contemplated pyrolyzers and the thermal oxidizers can have any suitable dimensions, but are preferably at least 5 meters long, and have a cross sectional area of at least 10 m 2 . In most contemplated embodiments, the thermal oxidizer has a length within 20% of the length of the pyrolyzer.

This application is a continuation-in-part of U.S. application Ser. No.11/757,189, filed Jun. 1, 2007, which claims the benefit of U.S.Provisional App. No. 60/810,382, filed Jun. 1, 2006.

FIELD OF THE INVENTION

The field of the invention is furnaces, and especially furnaces involvedwith liberating gas from solid fuel. (Class 110/229).

BACKGROUND

Pyrolysis employs high temperatures in a relatively oxygen freeenvironment to remove volatiles from solid fuels, as well as gases thatcan be released at high temperature from breaking down a feedstock.Depending on the feedstock, the volatiles can then be burned to produceusable energy.

It is known to pyrolyze innumerable different types of fuels, includingtrash, old tires, and other municipal wastes. As discussed incommonly-assigned U.S. patent application Ser. No. 10/517,023 to Walker,which is a national phase entry of PCT/US02/20362, filed Jun. 26, 2002,and U.S. Pat. No. 6,619,214 to Walker (September 2003), a typical wastetreatment system utilizing pyrolysis includes: (a) an input structurefor introducing waste; (b) a pyrolytic converter for breaking down afeedstock and generating waste gases; and (c) a thermal oxidizer thatburns the waste gases (also referred to herein as “syngas” or “syngases”). In preferred embodiments a portion of the heated gases can betransported back into an outer chamber of the pyrolyzer to help sustaincontinued pyrolysis of the feedstock.

It is known to dispose the pyrolyzer and thermal oxidizer in end-to-endconfigurations (see e.g., U.S. Pat. No. 5,586,855 to Eshleman (December1996); U.S. Pat. No. 5,653,183 to Hansen et al. (August 1997); U.S. Pat.No. 6,758,150 to Ballantine et al. (July 2004)), and in side-by-sideconfigurations (see e.g., U.S. Pat. No. 6,701,855 to Barba (March 2004);U.S. Pat. No. 6,745,707 to Suzuki et al. (June 2004)).

One advantage of the side-by-side configuration is that one can readilytransfer heat from the thermal oxidizer to the pyrolyzer. Barba '855,for example, teaches combusting the syn gases in a thermal oxidizer, andthen transferring a portion of the exhaust gas from the oxidizer backinto the pyrolyzer.

It is also known to dispose the pyrolyzer and thermal oxidizer in apiggyback configuration, where the pyrolyzer is disposed below thethermal oxidizer. The piggybacking can take within a common housing (seee.g., U.S. Pat. No. 4,084,521 to Herbold et al. (April 1978), U.S. Pat.No. 5,411,714 to Wu et al. (May 1995)), or without a common housing (seee.g., U.S. Pat. No. 4,802,424 to McGinnis et al. (February 1989))

Interestingly, however, no one seems to have appreciated that it can beadvantageous to transfer heat from the thermal oxidizer to the pyrolyzerwith a piggyback configuration. In two piggyback configurations using acommon housing, Herbold '521 and Wu '714, syngas produced in an innerchamber of the pyrolyzer is shunted back to an outer chamber of thepyrolyzer for burning. But that is not the same as burning the syngas ina thermal oxidizer, and then transferring the heat back to thepyrolyzer, for example by shunting the exhaust gas from the thermaloxidizer to the pyrolyzer. In a piggyback configuration without a commonhousing, McGinnis '424, there is no teaching at all of divertinganything back from the thermal oxidizer to the pyrolyzer.

Walker, Eshleman, Hansen, Ballantine, Barba, Suzuki, Herbold, Wu, andMcGinnis, and all other extrinsic materials discussed herein areincorporated by reference in their entirety. Where a definition or useof a term in an incorporated reference is inconsistent or contrary tothe definition of that term provided herein, the definition of that termprovided herein applies and the definition of that term in the referencedoes not apply.

Thus, there is still a need for systems, methods and apparatus thatdecrease the space requirements for a waste treatment system having apyrolyzer and a thermal oxidizer, while still retaining efficient heattransfer.

SUMMARY OF THE INVENTION

The present invention provides apparatus, systems and methods in which apyrolyzer and a thermal oxidizer of a waste treatment system are alignedin a partially or completely piggybacked fashion, and heat from theexhaust gas of the thermal oxidizer is shunted back to the pyrolyzer.Such configurations can advantageously decrease the floor space neededin a waste treatment facility, while still providing excellent energyefficiency.

As used herein, the terms “piggyback”, “piggybacking” and the likeshould be interpreted broadly as applied to a pyrolyzer and the thermaloxidizer combination, to include all situations where a vertical linewould pass through portions of both the pyrolyzer and the thermaloxidizer. Thus, all configurations where the thermal oxidizer or thepyrolyzer lies directly over the other are considered piggybacked, asare configurations where the alignment is more askew, but one of thepyrolyzer and the thermal oxidizer is still at least partially over theother. In preferred embodiments, one of the pyrolyzer and the thermaloxidizer is elevated relative to one another by at least 2 meters (m).In preferred embodiments the pyrolyzer is also distanced from thethermal oxidizer by less than 2 meters, and a saddle is disposed betweenthe pyrolyzer and the thermal oxidizer to prevent heat transfer.

Preferred pyrolyzers have an inner chamber that carries a waste stream,an outer chamber that provides heat to the inner chamber to sustainpyrolysis, and an outlet for release of syngas produced duringpyrolysis.

Preferred thermal oxidizers burn at least a portion of the syn gases ina hot flame from a natural gas burner, thereby producing hot exhaustgases. Thermal oxidizers also preferably have a conduit that transportsa portion of the hot exhaust gases back to the outer chamber of thepyrolyzer, which conducts heat to a waste stream in the inner chamber ofthe pyrolyzer to help sustain pyrolysis. Such conduits can have anysuitable configuration, including for example where the conduit extendsfrom sides (as opposed to the ends) of each of the pyrolyzer and thethermal oxidizer.

The pyrolyzer and the thermal oxidizer can have any suitable dimensions,but preferably the pyrolyzer and the thermal oxidizer are at least 5meters long, and have a cross sectional area of at least 10 m². In mostcontemplated embodiments, the thermal oxidizer has a length within 20%of the length of the pyrolyzer.

Various objects, features, aspects and advantages of the inventivesubject matter will become more apparent from the following detaileddescription of preferred embodiments, along with the accompanyingdrawings in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a pyrolyzer and a thermal oxidizer in apiggyback configuration.

FIG. 2A comprises a vertical end view of the piggyback configuration ofFIG. 1.

FIG. 2B comprises a vertical end view of an alternative piggybackconfiguration of a pyrolyzer and a thermal oxidizer.

DETAILED DESCRIPTION

FIGS. 1 and 2A generally depict a waste treatment system 100 having apyrolyzer 110 and a thermal oxidizer 140 in a preferred piggybackconfiguration.

Pyrolyzer 110 generally includes an outer housing 112, an inner housing114, a heated outer chamber 112A between the inner and outer housings,and an inner reaction chamber 114A in which pyrolysis occurs. Conveyormechanism 120 is disposed within, and passes through inner housing 114.Preferably, conveyor mechanism 120 is a screw type conveyor thattransports waste input as shown by arrow 118, through inner reactionchamber 114A as pyrolysis occurs.

Waste input 118 can accept any suitable type of waste, including forexample, municipal waste, and especially including dried waste fromsewage, municipal garbage, plastic scraps, scrap wood, oil impregnatedrags and refuse oils, scrap metal, and old tires and other articles ofrubber. Waste processed in the pyrolyzer exits the inner reactionchamber 114A as char, shown by arrow 124, via char outlet conduit 122.Processing of the waste also produces syn gases (pyrolysis waste gases),which exits the inner reaction chamber 114A via conduit 126, as shown byarrow 128, and then travels to the thermal oxidizer 140.

Thermal oxidizer 140 generally includes an input of syngas from conduit126, a burner 142, an exhaust gas return conduit 144, and an exhaust gasoutlet 148. The composition of the syngas can vary greatly as a functionof the waste being pyrolyzed, with syngas from pyrolysis of municipalwaste, for example, typically including hydrogen, carbon monoxide,methane, and lower molecular weight hydrocarbons, as well as nitrogenand carbon dioxide. A hot flame from a natural gas burner 142 ispreferably used to initiate combustion of the syn gases 128, therebyproducing hot exhaust gases 145.

Exhaust gas return conduit 144 shunts a portion of hot exhaust gases 145back to outer chamber 112A of pyrolyzer 110. Outer chamber 112A ofpyrolyzer 110 conducts heat to a stream of waste in inner reactionchamber 114A of pyrolyzer 110 to help sustain pyrolysis. Exhaust gasreturn conduit 144 can have any suitable configuration, including forexample where the conduit extends from sides (as opposed to the ends) ofeach of the pyrolyzer 110 and the thermal oxidizer 140. Any portion ofhot exhaust gases 145 not shunted to pyrolyzer 110 are carried out ofthermal oxidizer 140 by exhaust gas conduit 148.

Pyrolyzer 110 and thermal oxidizer 140 can have any suitable dimensions,but preferably pyrolyzer 110 and thermal oxidizer 140 are at least 3, 5,6, or 7 meters long, and have a cross sectional area of at least 8, 9,10, or 12 m². In most contemplated embodiments, the thermal oxidizer hasa length within 20%, 15%, or more preferably 10% of the length of thepyrolyzer. Also, as shown in FIG. 2A, pyrolyzer 110 is distanced fromthermal oxidizer 140 by less than 2, 1.5, 1 or even 0.5 meters, as shownby distance 132.

As shown in FIGS. 1 and 2A, pyrolyzer 110 and thermal oxidizer 140 havea piggyback configuration. It is contemplated that the piggybackconfiguration includes all situations where vertical line 170 (see FIG.2A) passes through portions of both pyrolyzer 110 and thermal oxidizer140. Thus, all configurations where thermal oxidizer 140 or pyrolyzer110 lies directly over the other are considered piggybacked. Pyrolyzer110 and thermal oxidizer 140 each have a bottom 116 and 146respectively, and in preferred embodiments, the bottom of one iselevated at least 2, 3, 4, or even 5 meters relative to the bottom ofthe other. FIG. 2B generally depicts an alternative piggybackconfiguration that is slightly askew, but one where the thermal oxidizer240 is only partially disposed over the pyrolyzer 210 such that avertical line 270 exists that passes through portions of both thepyrolyzer 210 and the thermal oxidizer 240.

FIGS. 1 and 2A also depict saddles 130A that support pyrolyzer 110 andsaddles 130B disposed between pyrolyzer 110 and thermal oxidizer 140.The saddle 130A, 130B allow expansion and contraction of the chambers astemperature changes, particularly along its length, without causing thechambers to buckle such as by bending, warping, or crumpling. Ceramicsaddles are particularly desirably under the pyrolyzer 110 because theyhave a relatively low coefficient of thermal conductivity, and wouldtend to inhibit the flow of heat out of the pyrolyzer 110.

It should be apparent to those skilled in the art that many moremodifications besides those already described are possible withoutdeparting from the inventive concepts herein. The inventive subjectmatter, therefore, is not to be restricted except in the spirit of theappended claims. Moreover, in interpreting both the specification andthe claims, all terms should be interpreted in the broadest possiblemanner consistent with the context. In particular, the terms “comprises”and “comprising” should be interpreted as referring to elements,components, or steps in a non-exclusive manner, indicating that thereferenced elements, components, or steps can be present, or utilized,or combined with other elements, components, or steps that are notexpressly referenced. Where the specification claims refers to at leastone of something selected from the group consisting of A, B, C . . . andN, the text should be interpreted as requiring only one element from thegroup, not A plus N, or B plus N, etc.

1. A device for pyrolytically treating waste, comprising: a pyrolyzerhaving an inner chamber that carries a waste stream, an outer chamberthat provides heat to the inner chamber to sustain pyrolysis, and aoutlet for release of syngas produced during pyrolysis; a thermaloxidizer that produces hot exhaust gases from oxidation of at least someof the syngas; a conduit that passes at least some of the exhaust gasesto the outer chamber of the pyrolyzer; and wherein the pyrolyzer and thethermal oxidizer each have a bottom and the bottom of one is at leastelevated 2 meters relative to the bottom of the other.
 2. The device ofclaim 1, further comprising the pyrolyzer and thermal oxidizer disposedsuch that a vertical line exists that passes through at least someportion of the pyrolyzer and at least some portion of the thermaloxidizer.
 4. The device of claim 1, wherein each of the pyrolyzer andthermal oxidizer are at least 5 meters long.
 5. The device of claim 1,wherein the thermal oxidizer has a length within 20% of a length of thepyrolyzer.
 6. The device of claim 1, wherein the pyrolyzer is distancedfrom the thermal oxidizer by less than 2 meters.
 7. The device of claim1, wherein the conduit extends from sides of each of the pyrolyzer andthe thermal oxidizer.
 8. The device of claim 1, further comprising asaddle disposed between the pyrolyzer and the thermal oxidizer.